High Performance InP-based Quantum Dot Light-Emitting Diodes via the Suppression of Field-Enhanced Electron Delocalization

To understand the exciton dynamics due to the electron delocalization in InP-based quantum dot light-emitting diodes (QLEDs), the exciton dynamics are systematically controlled in InP-based QLEDs through varying the shell thicknesses of InP/ZnSe quantum dots (QDs) and the effective electrical field (E-field) across the QDs. It is found that the field-independent energy transfer is effectively suppressed as the shell thickness increases. However, InP/ZnSe QDs with thicker shells only have limited benefit for suppressing the exciton transfer due to field-enhanced electron delocalization in films on electron transport layers or working devices. The field-assisted exciton transfer is mainly driven by the large E-field and field-enhanced electron delocalization in InP/ZnSe QDs. External quantum efficiency of 22.56% is achieved in InP-based QLEDs by reducing the effective E-field (at 2 V bias). The breakthrough luminance of 136 090 cd/m(-2) is achieved at a large bias of 7.2 V, due to the suppression of field-enhanced electron delocalization by the ultra-thick shell.